Treatment of real effluents from dyeing reactor: Experimental and modeling approach by adsorption onto chitosan

Abstract

This work aims to study the treatment (decolorization) of real industrial dyeing effluents originated directly from the dyeing bath, before entering the equalization tank (instead of treating the whole volume of wastewater) using chitosan beads as adsorbents. The addition of amido and imino groups on chitosan backbone through grafting reactions increased the adsorption capacity of adsorbents, while the cross-linking method made them capable of reuse for ten cycles at least without significant loss of their capacity (∼5%). The imino grafted derivative with a dosage of 5 g/L resulted in a residual dye content <1 mg/L, which is in accordance with the limitations of legislation. Swelling experiments demonstrated low swelling percentages (∼35%) for the prepared adsorbents. Equilibrium data were successfully fitted to the Langmuir–Freundlich model (L–F). Kinetic data were fitted to a proposed detailed mathematical model, based on the chemical structure of chitosan and on a valid single-component adsorbate approximation, resulting in diffusion coefficients of dyes in the triple dye mixture (both in simulated/synthetic and real effluents). A commercial form of activated carbon was used, to compare and confirm the high adsorption capacity and easy/successful regeneration of the prepared chitosan derivatives (through adsorption–desorption experiments in real effluent).